GEOLOGY AND OIL PROSPECTS OF THE SALINAS By WALTER A. ENGLISH. INTRODUCTION AND ACKNOWLEDGMENTS. The region discussed in this report lies in the southern Coast Ranges of California, extending from the country west of Salinas River eastward to the crest of the Diablo Range. East of this range is the San Joaquin Valley, along the west edge of which lie the largest productive oil fields of the State, though there are fields within the Coast Ranges farther south. In the area examined no productive wells have been drilled, but numerous seeps of oil occur and a number of wildcat wells have been drilled, so the region has been looked upon by many as presenting possibilities of future development. The present investigation was undertaken partly to procure data for the classification of public lands withdrawn from entry pending classification, and partly to determine areas in which the geologic conditions are favorable for prospecting so as to prevent useless expenditures in drilling dry holes in unfavorable areas. The field work on which the report is based was done during the field seasons of 1915 and 1916; about three months was spent within the area mapped. Throughout the field work the writer was assisted by Mr. William S. W. Kew, whose excellent aid is gratefully acknowledged. Thanks are due to the many ranchers, whose hospitality was a considerable factor in carrying on work in a thinly settled region. Acknowledgment is due particularly to Messrs. A. Pinkerton, Jean Garrissere, G. E. Huston, John Noreen, and Louis and Al Patriquin for information regarding wells that have been drilled. CONCLUSIONS. Though by far the larger part of the area examined has little to recommend it for wildcat drilling, certain areas appear to be well worth testing. The chief of these is the low anticline that extends southeastward from a point north of Bradley to a point east of San 1 The region along the edge of San Joaquin Valley east of the area here described has already been mapped by the Geological Survey and the results published in Bulletins 398 and 406. Miguel. A much smaller anticline in the Pleyto oil district and an area west of San Ardo, near the zone of oil-impregnated shale, also have possibilities, though these areas are deemed less favorably situated than the first mentioned. The Parkfield district and the anticline that crosses Vineyard Canyon near its head have received notice, from oil prospectors, but the writer believes them to be barren of oil. A description of each of these areas and the reasons for the above conclusions are given under the heading "Petroleum." PREVIOUS PUBLICATIONS. Although many geologists have visited this part of the Coast Ranges no accurate description of either the geology or the oil possibilities of the Salinas Valley region has been published. The fol-1 lowing chronologic review includes the principal papers. Among the earliest work done in the Coast Ranges was that of the geologists of the Pacific railroad surveys. Antisell1 describes the geology of Salinas Valley and the San Jose Range and the outcrops of bituminous rock in the Coast Ranges. At the present time this work has only a historical interest. Whitney, who was State geologist in early days, describes the geology of the Coast Ranges south of Monterey Bay and devotes sereral pages to oil possibilities. The trend of his statements was cal culated to throw cold water on an oil boom which was flourishing in California at the time he wrote. His conclusion that the beds dip too steeply and the structure is too broken for the development of a successful oil field, if applied to the mountainous part of the Coast Ranges, still holds with considerable force. In a report on petroleum by Goodyear in 1888 the asphalt occur rence on San Antonio River and the oil seepage near Parkfield are described. A summary of field notes by Fairbanks published in 1894 gives an interesting description of the geology of the Santa Lucia Range and a few notes on the area to the east. Notes on a well drilled near Table Mountain are given in the same volume. In a report published in 1901 Fairbanks and Watts describe briefly the geology of and oil developments in the Salinas Valley region. Eldridge during his work on the asphalt deposits of the United States visited the areas of asphalt-impregnated sandstones and 1 Antisell, Thomas, U. S. Pacific R. R. Expl., vol. 7, pt. 2, chs. 4, 6, 16, 1857. - Whitney, J. D., California Second Geol. Survey, Geology, vol. 1, ch. 5, secs. 1-2, 1865 3 Goodyear, W. A., California State Mineralogist Seventh Ann. Rept. pp. 85-89, 1885 Fairbanks, H. W., California State Mineralogist Twelfth Ann. Rept., pp. 356, 519-521, 1894. Watts, W. L., Oil and gas yielding formations of California: California State Min Bur. Bull. 19, pp. 143-145, 1901. shales west of San Ardo, and in the Pleyto district. His report 1 gives a short description of the geology and character of the deposits. A paper by Nutter," devoted largely to the water resources of the Salinas Valley, describes the low-dipping Tertiary beds in that valley. In 1904 Hamlin 3 described the formations present in the Salinas Valley and outlined its larger structural features. He devoted two pages to petroleum possibilities and recorded the test wells which had been drilled up to that time. No geologic map was published with this report, but through the courtesy of Mr. Hamlin the present writer has had access to a manuscript map prepared by him, which has proved very useful; and some data from it were used in the reparation of Plate XXVII. 4 In 1914 McLaughlin and Waring described the Salinas Valley and adjacent territory, and the map folio accompanying their report contains a geologic map of this region. 5 Besides these publications other papers that describe immediately djacent areas are of value in a study of the Salinas Valley region. LOCATION, TOPOGRAPHY, AND CULTURE. As is shown on the index map (fig. 35) the area investigated, all of which is within the drainage basin of Salinas River, lies in the Coast anges, west of San Joaquin Valley, about midway between San 'rancisco and Los Angeles. The geologic maps (Pls. XXVII, XVIII; fig. 36) show parts of the Priest Valley, Cholame, and San Miguel quadrangles. The Priest Valley and Cholame maps have been published, and topographic field work is now being done in the San Miguel quadrangle. All these maps are on a scale of approximately half an inch to the mile, with 100-foot contours. A 5-foot contour map of the area adjacent to Salinas River as far south as Bradley is also available. The area is mainly mountainous. The Diablo Range, the crest of which rises from 4,000 to 4,500 feet above sea level, forms the divide 1 Eldridge, G. H., The asphalt and bituminous rock deposits of the United States: U. S. Geol. Survey Twenty-second Ann. Rept., pt 1, pp. 410-411, 1901. 2 Nutter. E. H., Sketch of the geology of Salinas Valley, Cal.: Jour. Geology, vol. 9, pp. 330-336, 1901. 3 Hamlin, Homer, Water resources of Salinas Valley, Cal.: U. S. Geol. Suvrey WaterSupply Paper 89, 1904. 'McLaughlin, R. P., and Waring, C. A., Petroleum industry of California: California State Min. Bur. Bull. 69 and map folio, 1914. Arnold, Ralph, and Anderson, Robert, Geology and oil resources of the Coalinga district, Cal. U. S. Geol. Survey Bull. 398, 1910. Arnold, Ralph, and Johnson, H. R., Preliminary report on the McKittrick-Sunset oil region, Kern and San Luis Obispo counties, Cal.: U. S. Geol. Survey Bull. 406, 1910. Pack, R. W., and English, W. A., Geology and oil prospects of Waltham, Priest, Bitterwater, and Peachtree valleys, Cal.: U. S. Geol. Survey Bull. 581, pp. 119-160, 1915. Anderson, F. M., and Martin, Bruce, Neocene record in the Temblor Basin, Cal., and Neocene deposits of the San Juan district, San Luis Obispo County, Cal.: California Acad. Sci. Proc., 4th ser., vol. 4, pp. 15–112, 1914. between the Salinas and San Joaquin valleys. West of the Salinas Valley are a number of ranges, known collectively as the Santa Lucia Range, which separate the valley from the ocean. Parts of the Santa Lucia Range reach an altitude of over 5,000 feet a few miles from the ocean and are extremely rugged. The main ridges all FIGURE 35.-Index map showing location of the Salinas Valley-Parkfield area, Cal. have a marked northwesterly trend, determining a like course for the principal streams; and many of the smaller streams also trend in a northwesterly direction. A different type of topography, and one rather unusual in the Coast Ranges, is that between Salinas River and the San Andreas fault, to the east. In this area long, nearly |